System integration technology plays an important role for wireless communication development. And, a wireless communication capable of integrating a plurality of various communication frequency specifications is a popular research topic in recent years. Consequently, reliance of circuit design at the system integration side which enact the circuit exhibits a function of integrating a plurality of various communication specification is, therefore, the best candidate for this popular application. The most common circuit designs are demonstrated as follows:
FIG. 1A illustrates a duplexer 10a, comprises a first port 101a, a second port 102a, and a third port 103a; the first port 101a receives a first frequency f1a and outputs a second frequency f2a, the second port 102a outputs a first frequency f1a and the third port 103a receives a second frequency f2a. Alternatively, the duplex 10a is capable of bi-directional communication instead of frequency multiplexing.
FIG. 1B illustrates a diplexer 10b, comprises a first port 101b, a second port 102b and a third port 103b; where the first port 101a receives a first frequency f1b and a second frequency f2b, the second port 102b outputs a first frequency f1b and the third port 103b outputs a second frequency f2b. That is to say, the diplexer 10b is capable of frequency multiplexing instead of bi-directional communication.
The duplexer 10a or the diplexer 10b either illustrated in FIG. 1A or FIG. 1B can be capable of either bi-directional or multiplexing. Alternatively, the circuit characterized in bi-direction cannot simultaneously function as multiplexing, and the circuit characterized in multiplexing cannot simultaneously function as bi-direction. For microwave circuits, this is due to the conventional design and failure to using globally matching network.
FIG. 1C illustrates a circulator 10c having three input/output ports (P1, P2, and P3). In view of its counter-clockwise direction, (clockwise direction related description is omitted thereto), its input/output matrix is denoted as [S] as illustrated in FIG. 1D, where its input is the matrix [S]'s vertical axis and its output is the matrix [S]'s horizontal axis, is a very conventional circuit for the modern communication system, which enacts the signal being transmitted in enclosed system but only single frequency/band is allowed thus the satisfaction for the modern communication system cannot be met.